Ignition of internal combustion engines



Dec. 15, 1942. E. M. TRAMMELL, sR., ETAL 0 IGNITION OF INTERNALCOMBUSTION ENGINE Filed July 25, 1941 2 Sheets-Sheet l FIG.1. l6

- INVENTORS EARL M.-TRAMMELL, SR. EARL M.TRAMME| L, JR.

ATTORNEY E. M. TRAMMELL, $R., ETAL IGNITION OF INTERNAL COMBUSTIONENGINE Filed July '25, 1941 -Dec. 15, 1942. 2,305,208

2 sheets-sheet 2 INVENTORS EARL M.TRAMME| L ,SR. EARL M.TRAMMELL,JR.

AT TOR NEY conditions generally, become paramount.

Patented Dec. 15, 1942 IGNITION or INTERNAL COMBUSTION ENGINES Earl M.Trammell, Sr., and Earl M. Trammell,

In, St. Louis, Mo., assignors of one-third to Irving J. McGuire,Dolgeville, N. Y.

Application July 25, 1941, Serial No. 403,974

.15 Claims.

This invention relates to improvements in ignition of internalcombustion engines, and more particularly to methods of and means forimproving conditions of electric ignition of compressed fuel-air chargesin internal combustion engines.

Considerable design effort has heretofore been devoted to attempts tocontrol the conditions of incipient burning of fuel in internalcombustion engines, particularly in engines of compressionignitiontypes, as well as some others. It is also appreciated that variousdesigns of head and combustion chamber construction have been evolved inelectrically ignited engines and others, for the purposes of supposedlycontrolling conditions of flame propagation and trends of travel ofburning fuel. These efforts have assumed an increased importance due tothe prevalent tendency toward higher compression ratios in gasolineengines, wherein the problems of controlling detonation, controlling theexpansion ratio of the burning charge, and of improving electricignition The present invention may be stated as broadly directed towardimprovement of the factors mentioned.

Probably the most important objective of present improvements,considered from a structural point of view, is attained in an improveddesign, shaping and arrangement of parts of an electric igniter or sparkplug, such that, when certain parts adjacent the zone of actualignition, are disposed in a rapidly moving fluid stream, for example, ofmixture partly compressed in the cylinder, the movement of such streamin the region of the igniting arc, results in a reduction of pressurehead, accompanied by increase in velocity head of the gas particles inthe immediate region of first burning. This may be regarded as theparamount objective of present developments, since numerous physicalagencies may be employed in the cylinder, for attaining the desired jetor stream of rapidly moving gas particles.

Among the several additional objects of the invention may be stated theimproved combustion of an electrically ignited charge, by a novel methodand. means for directing an ignited stream of gas mixture at a highvelocity, into a centralized nal combustion engine, by a localizedmodifica- 55 tion of pressure in the immediate region of ignition,preferably in the main combustion space.

A further object of the invention is attained in an improved method ofand agencies for effecting a physical direction of a defined portion ofthe charge, first into the region of ignition, and thence depthwise intothe remainder of the charge, in a manner to produce a more efiicientcombustion of the whole charge with a minimization of detonation.

Expressed in terms of operational results attained, the presentdevelopments enable an increase in engine compression ratio, without anycomparable increase in detonation, or conversely expressed, enable areduction of detonation, in high compression engines equipped with thepresent improvements, when compared with similarengines not so equipped.

A still further object of the invention is attained in a more gradualand a more desirable direction of propagation of flame from the zone ofignition and incipient burning, throughout the mass of compressedcombustible mixture.

An additional important object of the invention is attained byestablishing, through a novel form of cylinder-and-piston constructionin conjunction with novel form of electrical igniter, a directional flowof a high velocity stream of the combustible mixture, and the directionof such stream, just, before,\ during and just after the time of igniti'n,\ina fixed relation with respect to the electrodes of the igniter,such as a spark plug of special design.

Somewhat ancillary to the foregoing objects,

the present improvements importantly attain a definite physical, asdistinguished from a chemical control of direction of flame propagation,such as often attempted heretofore by preliminary combustion of aportion of the charge, as in certain Diesel engines.

The foregoing and numerous other objects will be more clearly understoodas to the manner and degree of their attainment, from the followingdetailed description of certain preferred embodiments of the invention,particularlywhen considered in connection with the accompanyingdrawings, in which:

Fig. 1 is a fragmentary section in a plane parallel to the axis of thecylinder, of the cylinder, piston and head structure of one cylinder ofan engine to which the improvements are applied;

Fig. 2 is a fragmentary sectional view taken along line 22 of Fig. 1;Fig. 3 is a fragmentary section through the ignition zone and a portionof the combustion chamber of the cylinder of I suitable for use in andas a part of an engine embodying present improvements; Fig. 5 is an endelevation of the igniter or plug shown by Fig. 4; Fig. 6' is a sectionalelevation taken in an axial plane, showing the upper portion of thecylinder, head, spark plugs and piston of one cylinder of an air cooledengine of a type suitable, for example, for aircraft use, and to whichthe present improvements have been applied; Fig. 7 is a fragmentarysectional elevation of the structure shown by Fig. 6, and as viewedalong line 1-1 of Fig. 6, and Fig. 8 is a sectional elevation showingportions of the cylinder or head structure, piston'and igniter of themodified embodiment, and as viewed along line 8-8 of Fig. 6.

Referring now by characters of reference to the drawings, and first tothe embodiment identifled with Figs. 1 through 5, only the elementsnecessary for adequate illustration of present improvements have beenincluded in the drawings since the remaining elements of the engine areor may be of more or less conventional design. The structure illustratedincludes the upper portion of a cylinder, the cylinder wall or linerelement being indicated at l5, serving operatively to house the pistonindicated generally at Hi, the latter being preferably of a designparticularly adapted for present improvements, as will later moreclearly appear. The cylinder i5 is provided with cooling liquid jackets,the chambered portions of which are indicated at l1, and a detachablehead structure is mounted, through an intervening gasket 2 I, on thecylinder proper. Preferably two or more valves, generally indicated at22, cooper ate with seats 23 for the admission, for example, of acarbureted gasoline-air mixture and for the timed exhaust of burntgases, as will be readily understood. By preference the cylinder head 20is provided with chambered portions 24, 25, 26 for the circulation of acooling liquid, which, as may be desired, is in communication with thatwithin the spaces of the cylinder and adapted for circulation as by theusual rotary pump or the like (not shown).

Threaded into the head 20 is an electric igniter such as a spark plugindicated generally at 30, and consisting for example, 3|, a porcelainor other insulating body 32, and a. terminal for the reception of thehigh tension ignition lead (not shown). The special features ofconstruction of the plug will be later described.

.Referring now briefly to the elements of design for defining andphysically directing a high velocity stream of mixture across the regionof ignition of the charge, it will be noted that the piston I5, as bestappears from Fig. 2, is provided with an undercut or shouldered portion33 at one side of and slightly below its upper or outer margin. Thisundercut portion serves in operation to engage and cooperate with afixed bridge or inset 34, formed by preference of a metal having highheat-resisting properties such as tool steel, stainless steel or thelike, and fixed in position across this zone of the cylinder. In formthe element 34 as shown. is of a generally rectangular shaping, exceptthat its outer face is of a somewhat arcuate contour, this surface beingindicated at 35 (Fig. -2). As will also best appear from Fig.2, thecylinder wall or liner i5 is provided with a recess portion 36 whichconstitutes a hollow lateral extension of the liner l5 and the insidesurface 31 ofwhich conforms cl ly to the surface 35. The

of the usual metal shell projection 36 considered as a whole is of atrend axially of the cylinder and so, in a vertical cylinder, would beof vertical trend.

In the upper portion of the liner l5, it will appear that the hollowformation 38 is extended outwardly, and again inwardly toward the head,being constructed to constitute an arcuate nozzlelike formation 40 (Fig.1), the latter opening into the combustion chamber immediately adjacentto the ignition region as defined by the plug electrodes hereinaftermore particularly described. The nozzle 40 is formed by and between theconformed upper part of portion 36, and a small, preferablyrectangularly notched portion in the element 34, the preferred shapingof the recess or notch resulting in nozzle 40, being best shown by thesection of Fig. 2.

In the construction of the cylinder, the insert 34 may be assembled tothe cylinder in any suitable manner as by welding, or by the provisionof integral studs (not shown) on the block 34, engaging apertures in theadjacent upper peripheral portions of the cylinder, andbeing deformedinto holding engagement therewith. The holding expedients are notillustrated, since it is felt that either mode of attachment of theinsert 34 to the cylinder will be readily understandable.

It is a preference with the present improvementsto utilize a combustionchamber which is of substantial depth and which, by preference, issubstantially coextensive in transverse area with the full face of thepiston. Although the major principles of the present improvements may bepracticed with other forms of piston deviating considerably from thoseshown, it is a preference in the arrangement of Fig. 1, to provide thepiston head or face 42 with a central recess defined by a depressedpiston head portion 43 of partly spherical contour. Y

Referring now to a special form of plug or igniter designed to functionefficiently for ignition of the defined high velocity stream of mixtureresulting from features heretofore described, or otherwise created, thethreaded inner end 44 of the plug is or may be of itself of conventionalconstruction provided with the usual external threads, engagingcompanion threads (not shown) in the head portion 20. The plug connectorterminal is in electrical communication with a central electrode 45 andthe latter is surrounded, down to a zone just short of its inner end,with a preferably frusto-conical body of insulating material such as theporcelain or mica 46. It will be understood of course that the hightension lead from the distributor of the ignition source, such as amagneto or battery ignition system, is in electrical circuit with theupper terminal, and therethrough, with the central electrode 45 of theplug.

By preference the electrode 45 has metallically secured thereto a smallrectangular center plug electrode 41, the shaping of which best appears'from Fig. 5, and arranged in line with the electrode 45,- but suitablyspaced therefrom to form a spark gap or plurality thereof, are a pair ofgrounded plug electrodes 50 and 5|.

As will appear from Fig. 5, the electrodes 50, 41 and 5| are ofgenerally block-like form, and of unusual width, and bygreat-preference, the outer surfaces of the electrodes 50 and 5|, oralternate y the adjacent portions of the shell 44, are given a smoothand convex contouring, or streamlined shaping, each of these surfaceportions approximating by preference, the nose portion of a streamlinedobject. This shaping is done for the specific purpose of disposing therow of electrodes 50, 41 and directly in, and in line with the definedtrend of the high velocity stream of mixture expelled from the nozzleformation 40, above described in connection with Figs. 1 and 2.

It will have appeared from the description of the arrangement andshaping of the electrodes or adjacent spark plug portions that when ahigh velocity fluid stream is projected across the inner end of theplug, the stream so projected, will be divided, but with a minimum ofturbulence or frontal resistance, by the streamlined nose surfaces ofeither the electrode 50 or the electrode 5| depending upon exactplacement of the plug in the cylinder, and for which provision is madeas will later appear. The result of this division of the high velocitystream of mixture by the plug elements, is the creation of a cavitationeffect within both of the spaces indicated at 52 between the ad jacentelectrodes. Otherwise explained, the pressure head component of totalpressure otherwise existing because of cylinder compression, in theregion of the plug and elsewhere, is in the latterregion converted insubstantial part to a velocity head, thus effectively reducing momentarystatic pressures in the immediate region of the plug electrodes. Sincethe relation of electrical resistance to arcing, in respect to gaseouspressures, is well known, it will be obvious that the reduction ofpressure head in the zones 52 between the electrodes, will operate toattain a number of advantages. For example, with an ignition coil of agiven step-up ratio and number of turns of secondary winding, constantinductance, etc., the gap between igniter electrodes may be increasedwith certainty of ignition because of reduced gas pressure across thegap. There being thus permitted a greater spark gap, a measurableincrease in fuel economy will result.

Incidentto the movement of the defined stream of the mixture across theelectrodes prior to and at the time of ignition, there results thefurther obvious advantage of self-cleaning of the plug electrodes and alessened tendency to fouling thereof due, for example, to carbonaccumulation.

It will have appeared from the foregoing description of eflect ofmovement of the high velocity stream of mixture across the electrodes,that the cavitation effect resulting in the zones 52 approximates whatis sometimes popularly referred to as a venturi action. Since, however,the relation between pressure head and velocity head is more accuratelyexpressed by the well known Bernoullitheorem, and since the situationexisting in the region of the ignitor is thereby ac- I countedfor, or bya corollary of such theorem, this'conditio'n and the effect attained is,for convenience,-referred to as 'a Bernoulli effect.

' As thus far described, the three aligned elements of the plug origniter, viz. 50, 41 and 5|, have been referred to as electrodes, since,depending upon the.relative spacing of these elements, the ignitionspark may occur in either of the zones 52, necessarily across the gap ofleast resistance. It is, however, important to consider that it is notnecessary to utilize, solely, the electrodes as agencies forattainingthe Bernoulli effect in the region of ignition. For example, byspacing'the center electrode 41 somewhat more closely to element than toelement 5|, ignition will invariably take place by arcing betweenelectrodes 41 and 50. Underthese conditions element 5| ceasesefiectively its function as a plug electrode, and may be regarded solelyas a physical agency, when presented nearest the point of origin of thefluid jet-forming agencies such as channel 40, and under such conditionselement 5| serves solely the purpose of a deflector. It is accordinglydistinctly within the purview of the present developments, to employ adeflector element to attain the described cavitation effect in theregion of the ignition are, by means other than the electrodesthemselves. In the example just described, one of the outside elements(50 or 5| according to location of the plug in the cylinder) serves thispurpose.

There should be mentioned for completeness a fact which will clearlyappear from the drawings and foregoing description, namely, thepreference for such an arrangement of spark plug, plug electrodes andstream deflecting agencies, that the spark discharge occurs in adirection along or parallel to the trend or defined direction of thehigh speed jet of mixture heretofore described. It is to be noted as oneof the advantages of the special form of plug described, that when theplug is properly oriented in the cylinder as by indicia for thispurpose, hereinafter described, the arc and moving jet of fluid will becharacterized by about the same direction. This feature is of someadvantage over the conditions prevailing were a conventional plug to beused, and the engine provided with a suitable form of jet-deflectingagency either on or near the plug. In the latter arrangement, thedirection of the jet would be normal or at right angles to the line ofspark discharge, and hence would exhibit a marked snufling tendency,which is not noticeable with present improvements.

Proceeding now to a more complete discussion of the preferred agenciesby which the high velocity stream of mixture is caused to move acrossthe electrodes as described, it may be noted that the relation betweenthe insert 34, channel or nozzle 40 and element 36 is such that, as thepiston I6 is moved upwardly on its compression stroke, (assuming forexample the improvements to be embodied in a four cycle engine) therewill be a certain portion of the fluid mixture under compression,entrapped in the space between shoulder 33 and the shouldered underportion of bridge 34, during such outward or upward movement of thepiston toward the cylinder head. As soon, however, as the pistonapproaches its top center position or more advanced firing position asdesired, thus bringing the shoulder 33 and bridge 34 together, theportion of the charge entrapped therebetween will thereupon be releasedand expelled into and through the channel 40, and because of theprevious confinement of this charge portion and the relatively smallsectional area of the passage formed by the nozzle structure, thisstream, which is of a width only slightly greater than that of the plugelectrodes 50, 41 and, will be expelled at high velocity in a line withand just ahead of this row ofelectrodes. From this it will be seen thatthe described jet-forming structure of the cylinder and piston or onethereof, coacts with the igniter, at the time of ignition, to attain ahigh-velocity stream of burning mixture, the rate of projection of whichis at least equal to linear piston speed, and may be of greater speedbecause of some separate initial compression of the small chargeentrapped just before its release.

There will now be considered the effect on ignition and the subsequentcomplete burning of the charge confined in the main portion of theclearance between the piston and head, as attained by the piercingaction of the defined stream of now-ignited combustible mixture. In

most if not all engines of prevailing type equipped Accordingly, in theabsence of some physical,

means serving to define a trend of movement of the first-kindled burningparticles, there can exist no defined trend ordirection of flamepropagation. According to the best information available it appears thatin the prevailing absence of any specific physical agency fordetermining such trend, burning will first take place peripherally orperimetrally of the combustion chamber, often first in the relativelyshallow portions thereof, thus resulting in undesirable detonationeffects. In the utilization of present improvements it will appear fromthe location of the jet or nozzleforming elements in relation to bothpiston and head, that the high-velocity stream of initially burningcharge is propelled definitely toward the center, and preferably alsothe deepest portion of the clearance or combustion chamber. Thus, as faras is known to applicants, there is created for the first time apositive control by a distinctly physical agency, of trend of flamepropagation. The movement of the stream emanating from thenozzle-forming elements 40 and 4|, being inwardly and approximatelydiametrally of the combustion chamber, the initially kindled particlesof mixture projected as they are at high velocity directly to a centralzone of the whole combustible mass, will result thereafter in a flameextension from the center or deepest'portion of the charge outwardly,with reasonable uniformity, toward the marginal portions of the confinedcharge. By the time, however, that the outermost portions of the chargehave been completely fired, some recession of .the piston and hence someexpansion has taken place in a manner to render crank angles morefavorable for continued expansion without detonation, and with aminimum'heat loss by wiping action of flame on the cooled upper cylinderwalls.

From the foregoing it will have appeared that the present improvementsserve to attain a definite physical control of trend and manner of fiamepropagation through the whole. mass of charge, and that in utilizationof the present developments, by controlling the more intense earlyburning stage of the charge so that it is kept in or near the center ofthe mass of mixture instead of the flame predominantly wiping the insideperimetral combustion "chamber surfaces. This older and prevailingpractice results in deleterious effects on metal surfaces andlubrication, and causes relatively higher heat losses to the jacket orribs, which effects are all markedly minimized according to the presentdesign.

In order to minimize or obviate any destructive tendency of localizedheating effects in the region of the nozzle-forming elements, such asmight. otherwise occur during expansion of the charge on the workingstroke of the piston, it is preferred to provide a relatively thin wallsection 53 (Fig. 1) in the region of the passage 40. This relativelythin wall separating the nozzle from the cooling jacket fiuid in thiszone, facilitates heat transfer with a locally augmented cooling effectin such manner that any tendency toward an accentuated heating effect inthis region will not damage the metal parts even over a long period ofoperation.

Itwillbenotedthatthereareanumberof structural possibilities, varyingfrom the few selected embodiments, for producing the high velocitystream of mixture across the igniter electrodes and projecting thestream into the center of the charge of fuel mixture. It will beapparent that the nozzle-forming structure may be constituted eithersolely by special construction of the piston, or solely by a particularconformity of the cylinder wall element, or by both of such cooperatingmembers.

As an example of an embodiment of the present improvements in an engineof somewhat different type, such as an air cooled aircraft engine, Figs.6, 7 and 8 will be found supplementally instructive. The function andprinciples of operation are or may be similar to those set forth abovein connection with the structure of Figs. 1 through 5, but it may benoted for completeness that in the modified form the cylinder structureindicated at is provided with an integral head portion indicatedgenerally at H, both cylinder and head being provided with preferablyintegral cooling ribs or fins 62 on the cylinder, and 63 on the head. Inthis arrangement a piston 64 may be provided with a relatively fiat topor head 85, since the cylinder head ii is substantially arched or domedto provide a deepened central portion of the combustion space definedbetween the piston and head ii. In the latter are operatively seated,inlet and exhaust valves designated generally at 66 and GLandcooperating respectively with seats and H.

Although dual ignition or in fact any desired reasonable number ofigniter elements may be employed in either of theembodimentsillustrated, or others, dual ignition is shown as embodied inthe air cooled cylinder, the two plugs being each indicated at 30, sincethey are or may be similar to the single plug Iii in the embodiment ofFig, 1. The construction and arrangement of electrodes are or may be asheretofore described. In the modified form of Figs. 6, 7 and 8, theigniters 30 are disposed diametrally opposite each other, and in avertical cylinder would be arranged horizontally in a zone in or nearthe juncture of the head and cylinder body. In this zone, the cylinderstructure is undercut or recessed somewhat as indicated at 12, therecesses I2 terminating inwardly in a shoulder 13 just below the plugrecess. The piston I4 is provided with similarly shaped, cooperatingshoulders l4.

Each of the recesses 12 is in this case, formed in a projection 15,(Fig. 8) extending inwardly" of the normal cylinder wall, and each ofthese recesses is formed as a channel of a trend axially of thecylinder, 1. e., a vertical trend in a vertical cylinder. Theprojections 15 are individually provided with a planar, inwardlypresented face 16, with which cooperates a companion planar face 11 onthe piston 84, the mating plane between the surfaces I6 and I1 chordwiseintersecting the cylinder space. It will have appeared from thestructure just described, that the eflect in operation is closelysimilar to that attained in the structure of Fig. 1. except for thefact, obviously, of the provision of two sets of agencies in diametrallyopposite zones of the cylinder for simultaneously collecting,compressing, confining and then sharply injecting the high speed jets ofcompressed fuel mixture, each jet being projected at high velocityacross the ignition zone of the adjacent plug 30.

It will appear that, in the arrangement of Fig. 6, as the piston movesupwardly on its compression stroke, portions of the charge will beentrapped at opposite sides of the cylinder, in each of the channels 12and between the cooperating shoulders 13 and H. Just before the pistonattains top center position, or optionally, some other lower point inpiston travel'at which ignition occurs, the charge collected betweenparts 13 and 14 and in the nozzle-forming passage 12,

will be forcibly delivered across the electrodes of the igniters 30,thence by the curved upper surface of the recess 12 indicatedparticularly at 80 (Fig. 6) these high velocity, now-ignited chargestreams will be propelled depthwise, diametrally and more or lessdirectly to the center of the burning mass, all with results andadvantages heretofore described.

Since it is of course desirable to be assured of the correct alignmentof the igniter electrodes, and other parts, in keeping with the trendsor directioning of streams of igniting charge, it is desirable toprovide both the plug and the adjacent exterior elements of the cylinderor head with suitable indicia by which the correct position of the plugin the cylinder is assured. Such indicia may for convenience consist ofsuitable arrows, pointers, or other provisions, such for example "as thearrow 8| on the shell of the plug, and projection 82 (Fig. 6), on thecylinder or head casting. In the manufacture of the plug,

the arrow 8| will of course be located on theshell of the plug in suchmanner that when brought to register with the projection 82, theelectrodes will be suitably aligned with the nozzle-forming elements ofthe cylinder.

It will have appeared that the foregoing embodiments of the inventionserve to attain each and all of the several advantages and objectshereinabove-specifically stated, as well as those implied from the moredetailed description.

Although the present disclosure has described the invention by detailedreference to specific structural embodiments, the description is to beunderstood merely as illustrative, and not as limiting the invention,since various changes may be made in the parts, their combinations andthe manner of their utilization without departing from the full intendedscope of the invention as defined by the claims.

We claim:

1. The described method of operating an internal combustion engineprovided with an electrical igniting agency in a combustion chamber,which consists in projecting a defined ignitable fluid stream across theigniting agency and parallel to the course of the ignition discharge,thence substantially directly into approximately the central portion ofthe combustion space, substantially at the time of'ignition, and inreducing the pressure head of the fluid in the immediate region ofignition at the time of ignition discharge.

2. The described method of operating an internal combustion engine ofpiston-and-cylinder type provided with an electrical igniting agency ina combustion chamber, which consists in entrapping within the cylinder,a portion of the cylinder charge, and thereafter projecting saidentrapped portion of fluid at a substantial velocity across the igniterand therebeyond, to a zone substantially inwardly of the wall portionsdefining the clearance, firing the charge by an arc, and so directioningthe arc that resistance thereto by the charge, is' minimized by the saidstream of projected fluid.

3. The described method of igniting a charge of combustible fluids in aninternal combustion engine of piston-and-cylinder type, which consistsin projecting a relatively high-velocity, nonturbulent stream of thecombustible fluids along such'a course that substantially the highestvelocity portion of said stream traverses a zone of electric ignitionigniting said stream by an arc of fixed direction approximatelyparalleling said high velocity stream portion, thence impelling saidstream into a zone substantially centrally and transversely of thecombustion chamber.

4. The described method of operating an internal combustion engine ofpiston-and-cylinder type provided with electric ignition, which consistsin projecting a jet of gas substantially diametrally of the medialportion of the combustion chamber and s0 directioning the jet of gasthat its stream is of substantially rectilinear trend, and igniting thecharge of combustiblefiuid in the cylinder by an electric discharge, andimparting a definite trend to the ignition are so that it occurs along apath parallel to and distinctly within the said jet of gas.

5. The method recited by claim 4, further characterized by the step ofcausing said electric discharge for ignition purposes, in a zone closeto the point of projection of the jet of gas into the combustion space.

6. The described method of operating an internal combustion engine ofpiston-and-cylindertype equipped with electric ignition, which consistsin confining a minor portion of the cylinder charge between the pistonand cylinder during the compression stroke of the piston, projectingsaid confined portion in the form of a jet, into a substantiallyintermediate zone of the cylinder charge while undergoing compression,in utilizing the velocity head of said fluid jet to create a Bernoulliefiect between the ignition electrodes during the period of ignition andin causing an electrical ignition discharge substantially parallel tosaid fluid jet in the region of the electrodes.

7. The described method of operating an electrically ignited internalcombustion engine of piston-ancl-cylinder type, which consists inconfining a relatively minor portion of the compression charge withinthe cylinder, between the piston and cylinder during a compressionstroke of the engine, projecting said confined portion of the charge inthe form of a relatively high velocity jet directed to the central zoneof the combustion space, and in igniting the substantially compressedcylinder charge, by an electric discharge, and causing said discharge tooccur in a direction along rather than across said jet, as in a portionof reduced pressure within the projected fluid jet.

8. In an internal combustion engine, a cylinder, a piston operabletherein, means formed by adjacent coacting portions of the cylinder andpiston to entrap arelatively minor portion of the cylinder charge and toexpel said entrapped charge portion in jet form into the combustionspace, an ignition member in the path of expulsion of said entrappedcharge, and means associated with the ignition member for dividing saidjet in the immediate region, and at the time of the igniting arc, saidmember and means being arranged to establish the igniting arc insubstantially a coaxial relation to the jet, whereby said jet promotes,rather than exhibits any tendency to snuff the ignition arc.

9. In an internal combustion engine, a cylinder, a piston operabletherein, means formed by adjacent coacting portions of the cylinder andpiston to entrap a relatively minorportion of igniter being fixedly solocated with respect to the means aforesaid, that the electrodes aresubstantially aligned with the jet resulting from expulsion of saidentrapped charge.

10. In an internal combustion engine including a cylinder and a pistonoperable therein, means 10 for impelling a relatively minor portion of apartly compressed cylinder fluid, in a defined stream at a substantialvelocity, said means being so located and directioned as to impel saidstream substantially medially of the combustion space,

an electric igniter, and an element in the region of the igniter, formedto create, in coaction with said stream, and with low turbulence, arelatively reduced pressure head in the region of ignition, said igniterand element being arranged to establish a substantial coincidence of theline of ignition arc with the source of said stream in the region ofignition.

11. In an internal combustion engine including a cylinder and a pistonoperable therein, 5

means for impelling a relatively minor portion of a partly compressedcylinder fluid, in a defined stream at'a velocity substantially equal tothe then-prevailing linear velocity of the piston,

said means serving to impel said stream substantially medially of thecombustion spacefiand an electric igniter, including a pair ofelectrodes spaced along the course of said stream, at least one of saidelectrodes being formed in part of a tapered cross section, whereby tocreate a region of relatively reduced local pressure in the immediateregion of the electrodes and at the time of ignition,

12. An electric igniter for an internal combustion engine, the igniterhaving an element adapted to extend into the combustion space of theengine, and shaped to provide a portion of tapered cross section,whereby when disposed in a high velocity jet of fluid in the cylinder,said element serves to reduce the pressure head in the region in whichignition occurs.

13. In an internal combustion engine, a cylinder, a piston operabletherein, an electric igniter including a pair of electrodes, means forcausing a stream of ignitible mixture to move across the nfiion of theelectrodes and generally parallel to the direction of discharge at thetime of ignition, an element of streamline section arrangedsubstantially in the line of said stream, adapted under the influence ofthe stream, to modify the fluid pressure head in the region of theelectrodes at the time of ignition, and means on an exterior portion ofthe igniter, enabling location of the igniter in the cylinder topreserve a constant relation between the direction of said mixturestream and the igniter electrodes.

14. An electric igniter for an internal combustion engine, and includinga pair of electrodes between which ignition sparking occurs, one of saidelectrodes being of tapered section and so shaped as to minimizeresistance thereof to a flow of fluid in the direction of ignition arc,whereby when the igniter is disposed in a high velocity jet of fluidundergoing compressiom-said electrode serves to reduce the pressure headin the region of ignition,

15. A spark plugfor internal combustion engines, including a pair ofelectrodes normally adapted to extend into the combustion space of theengine, the plug being so formed as, when energized, to provide anigniting arc of'deflnite direction or trend with respect topredetermined portions of the combustion space of the engine, andindicia provided so as to be visible exteriorly of the plug, fordirectionally positioning the plug into the combustion space of theengine.

EARL M. TRAMMELL, an. EARL M. 'rasmmm, JR.

